{
  "family": "regrun",
  "sample_count": 45,
  "category": "trojan",
  "description": "Trojan:Win32/Regrun is a heuristic detection utilized by antivirus engines to flag executables that aggressively and suspiciously modify the Windows Registry—specifically the 'Run' and 'RunOnce' keys—to establish persistent execution upon system boot.<br><br><b>Understanding Regrun</b><br>To the user, this is a standard security alert. For a security analyst, a 'Regrun' detection highlights a critical behavioral anomaly. While legitimate software uses the Registry Run keys (`HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Run`), malware abuses them almost universally (`T1547.001`). The AV engine triggers this heuristic when a newly dropped, unknown executable attempts to forcibly insert itself into these autostart locations, often using randomized filenames or attempting to overwrite existing, legitimate entries.<br><br><b>Execution and Evasion Strategies</b><br>Because it is a behavioral heuristic, the underlying payload could be anything: adware, a RAT, or a botnet agent. The infection vector varies wildly. The critical action is the persistence mechanism. The malware drops its payload (often into `%AppData%` or `%Temp%`) and immediately calls the Windows API (`RegCreateKeyEx`, `RegSetValueEx`) to ensure it survives a reboot. Advanced variants may utilize 'Registry hooking' to intercept attempts by security software to read or delete the malicious Run key, essentially blinding the AV to its presence.<br><br><b>Indicators of Compromise & Impact</b><br>The impact depends on the payload that achieved persistence. EDR platforms are highly effective at detecting this behavior, logging the specific process that initiated the unauthorized registry modification. Incident responders should immediately audit the `Run`, `RunOnce`, `RunServices`, and `Userinit` keys within the Registry. The presence of randomly named executables pointing to temporary directories within these keys is a definitive IoC.",
  "cta": "Published by the SystemHelpdesk team.",
  "aliases": [],
  "enrichment_level": "expert-seo",
  "faq": [],
  "faq_count": 0,
  "mitre_attack": [
    "T1547.001",
    "T1204.002",
    "T1059.003",
    "T1036.005",
    "T1112"
  ],
  "cisa_advisory": null,
  "last_updated": "2026-06-09",
  "mitre_attack_detail": [
    {
      "id": "T1547.001",
      "name": "Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder",
      "tactic": "Persistence"
    },
    {
      "id": "T1112",
      "name": "Modify Registry",
      "tactic": "Defense Evasion"
    },
    {
      "id": "T1204.002",
      "name": "User Execution: Malicious File",
      "tactic": "Execution"
    },
    {
      "id": "T1059.003",
      "name": "Command and Scripting Interpreter: Windows Command Shell",
      "tactic": "Execution"
    },
    {
      "id": "T1036.005",
      "name": "Masquerading: Match Legitimate Name or Location",
      "tactic": "Defense Evasion"
    }
  ],
  "containment_steps": [
    "Isolate the endpoint to prevent the underlying payload (which has now attempted to establish persistence) from communicating with its C2 server.",
    "Utilize EDR or offline registry analysis tools (like Autoruns) to identify and delete the malicious entries from the Registry Run keys.",
    "Locate the executable path referenced in the malicious Run key and quarantine the associated binary from the file system.",
    "Capture a forensic memory image to analyze the active process that initiated the registry modification and determine its true capabilities."
  ],
  "what_to_avoid": [
    "Do not assume the threat is contained just by deleting the dropped file; the malware may have injected into memory and will rewrite the Registry key.",
    "Avoid rebooting the machine during triage, as this will trigger the persistence mechanism and potentially execute secondary payloads."
  ],
  "target_industries": [
    "Global / Opportunistic"
  ],
  "motivation": "Opportunistic",
  "threat_actors": [
    "Unknown / Cybercriminal"
  ],
  "target_geographies": [
    "Global"
  ]
}